Treating someone as if they are less intelligent or important than you, in a condescending way.
From Latin 'patronus' (protector, father figure). The word originally meant 'treating someone as a patron treats a client'—with assumed superiority born from the power difference.
The British spelling 'patronising' vs. the American 'patronizing' is itself a tiny example of linguistic patrimonialism—British spelling conventions were considered more 'proper' and sophisticated, which is delightfully ironic since the word itself warns against exactly that kind of snobbish attitude.
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